This invention pertains to the loading of an electric furnace for founding to a high casting temperature metal alloys which are highly subject to oxidizing in order to supply foundry molds. In particular, it pertains to the loading of a graphite rod electric furnace, with openings sealed shut, this furnace being filled with pressurized argon that is monitored above the metal alloy bath by an inner argon current.
This furnace, which is equipped with a casting channel that can be directly connected to the supply orifice of a foundry mold, is of the tilting kind so as to vary the slope of the casting channel between a metal alloy receiving position for reheating and founding and a mold supply position for transferring the metal alloy from the furnace to the molding cavity.
The previously mentioned metal alloys to be made in such a furnace are those which are cast at a temperature that is at least equal to 1,400.degree. C. and that are extremely sensitive to oxidation. For instance, they are iron, nickel, chromium, or iron, chromium nickel, cobalt, austenite-based super-alloys or nickel-based or cobalt-based super-alloys, which contain less than 20% iron, or for instance refractory nickel, chromium, iron-based alloyed steel with more iron than the super-alloys, or ordinary steel. Super-alloys and refractory steel or strongly alloyed steel are used to mold parts designed to resist high temperatures (for metallurgical furnaces, mechanical, the aerospace industry, etc.).
Such a furnace undertakes slow founding, by radiating heat from its graphite rod. It was selected for founding such alloys over more popular founding devices which are more conductive to quick founding, such as induction furnaces or at least solid or liquid fuel furnaces, because of its ability to produce repeatedly and reproducibly metal alloys, especially well-defined super-alloys, by avoiding any pollution, especially air pollution. It also avoids undesirable solid, liquid or gaseous elements such as those which common furnaces heated with solid or liquid fuel might introduce inside a metal bath.
However, the industrial need to supply foundry molds with liquid metal at a fast rate is not very compatible with the use of such a slow founding furnace. Indeed, such a furnace, with a limited founding capacity, 500 kg for instance, requires several hours to found such a quantity of solid metal alloys introduced in the shape of ingots, and it is felt that this furnace is unusable in industrial applications.